Navigational guide system



Oct. 8, 1946. J. H. HAMMOND. JR 2 0 NAVIGATIONAL GUIDE SYSTEM Filed Feb. 5, 1943 9 Sheets-Sheet 1 INVENTOR JOHN HAYS HAMMOND, JR.

&3, 1946- J. H. HAMMOND, Jh I 2,408,348

NAVIGATIONAL GUIDE SYSTEM F iled Feb. 5, 1943 9 Sheet s- Sheet 2 TWO 3! BEAT PHASE DETECTOR IMPULSE ERATOR REPEATER FREQUENCY 2 MODULATOR 0 t N 3 6' U L [L T i m e INVENTOR JOHN HAYS HAMMON 0, JR.

Oct 1946- .1. H. HAMMOND, JR 2,408,843

NAVIGATIONAL ,GUIDE SYSTEM Filed Feb. 5, 1945 9 Sheets-Shet :5

INVENTORY JOHIN HAYS HAMMOND,JR

m v N Oct. 8, 1946. J. H. HAMMOND. JR

NAVIGATIONAL GUIDE SYSTEM 9 Sheets-Sheet. 4

Filed Feb. 5, 1943 INVENTOR JOHN HAYS HA MMND,JR.

0st. 8, W46.

J. H, HAMMOND, JR NAVIGATIONAL GUIDE SYSTEM Filed Feb. 5, 1943 9 Sheets-Sheet 5 INVENTOR JOHN HAYS HAMMOND,JR.

Oct. 8, 1946. J. H. HAMMOND, JR 2,403,348

' NAVIGATIONAL GUIDE SYSTEM Filed Feb. 5, 1943 9 Sheets-Sheet 6 INVENTOR 194% J. H. HAMMOND, JR 43 NAVIGATIONAL GUIDE SYSTEM Filed Feb. 5 1943 9' Sheets-Sheet 7 lNVENTOR JOHN HAYS HAMMOND,JR.

0d; 19416- v 4.1-1. HAMMO-ND, JR 2,403,843 I NAVIGATIONAL GUIDE SYSTEM Filed Feb. 5, 1943' 9 Sheets-Sheet iNVENTOR ,JOHN HAYS mmmowcnm.

Oilfi- & 3946- J. H. HAMMOND, JR

NAVIGATIONAL GUIDE SYSTEM Filed Feb; 5, 1945 9 Sheets-Sheet 9 z 2 f 4 a M, L h n V. I q 1 2 PS M .ll 1 W 1 E 1 1 m L LTLT 0 i. M q. 3 y 2 8 4 J M 2 a, w u w 7 g P w q 0 a 8 2 2 INVENTOR aux-m HAYS HAMMONILJR.

Patented ct. 8, 1946 sass rm" rate NAVIGATIONAL GUIDE SYSTEM John Hays Hammond, Jr., Gloucester, Mass, assignor to Radio Corporation of America, a corporation of Delaware 12 Claims.

This invention relates to navigational systems and more particularly to a system for determining the position of navigational markers by means of radio reflection.

The invention provides means for locating the position of fixed markers by sweeping the area with a radio beam and receiving the radio wave reflected from the marker on a position indicating device.

The invention also provides means for radiating a plurality of radio waves which are selectively reflected by different set of markers.

The invention further provides means for reflecting the radio waves from the marker in a fixed direction, so that a definite angular position may be determined.

The invention also provides means for varying the reflective properties of. the marker so that a different code signal is produced by each marker thus serving to identify the individual markers.

The invention also provides means for varying the number and configuration of the markers so that a definite code signal will be produced as the radio beam sweeps the marker system.

The invention further provides means for placing a system of reflectors upon ships so that the identity and the direction in which the ship is travelling may be ascertained from the reflected waves.

The purpose of this invention is to enable the navigator of a vessel approaching the shore to ascertain his location with reference to known fixed points along the shore line.

'The invention also consists in certain new and original features of construction and combinations of parts hereinafter set forth and claimed.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which Figure l is a sectional elevation of the pilot house of a vessel equipped with the present invention,

vFigure 1a is a block. diagram illustrating the essential features of a system embodying the present invention,

-Fi gure 1b is a curve illustrating the operation of the system of Fig.'1a,

Figure 2 is a schematic diagram of the transmitting and receiving circuits,

Figure 3 shows a modified form of coupling mechanism,

Fig. 4 is a diagrammatic illustration of an impulse generator forming part of the receiving circuit,

Figure 5 is a plan View of the position indicator shown in Figures 1 and 2,

Figure 6 is a plan view of one type of reflecting equipment,

Figure '7 is an elevation of the reflector depicted in Figure 6,

Figure 8 is a plan View of a harbor provided with a plurality of reflecting systems,

Figure 9 illustrates a modified type of transmitting and receiving apparatus,

Figuresv 10 and 11 are schematic diagrams of modified forms of the combining circuit,

Figure 12 is a schematic diagram of an audible indicating system,

Figure 13 is a side elevation of another modified form of reflecting system,

Figure 14 is a detail view of the cam used in the system of Figure 13,

Figure 15 is a plan View of a directive reflecting system, and

Figure 16 is a plan view of a vessel illustrating a vessel identification system.

Like reference characters denote like parts in the several figures of the drawings.

In the following description parts will be identified by specific names for conveniencabut they are intended to be as generic in their application to similar parts as the art will permit.

Referring to the accompanying drawings, and more particularly to Figure 1, the pilot house of a vessel is indicated at -l i. Rotatably mounted on the roof of the pilot house H is a directional horn antena transmitting and receiving system i2, which is rotated by a driving mechanism It, and is connected to a combined radio transmitter and receiver it. The receiver l lis connected by a cable It": to an oscilloscope l6 mounted in the steering wheel pedestal ll.

The oscilloscope i6 is in the form of a cathode ray tube having a fluorescent screen I32 (Figs. 1a and 2) with an adjustable graduated screen I63 (Figs. 2 and 5) through which the cathode ray spot [6a (Fig. 5) is viewed. The system is designed so that the angular position of the spot ltd on the screen I32 indicates the direction of the object from which the reflected waves are received and theradial distance of the spot Ito I to the distance of the vessel from such object.

The system for accomplishing this is indicated in block diagram in Fig. la as embodying a directional short wave transmitting and receiving antenna system i2 which is rotated in azimuth on a shaft 31. A two phase repeater i 8 is connected to produce in a repeater l8a, two phase current having a frequency corresponding to the speed of rotation of the shaft 3|. This current is supplied to deflection plates MI and I42 of the cathode ray tube !6 and causes the spot lfia to maintain an angular position corresponding to the angular position of the antenna system I 2. The spot hid, however, only appears when a reflected wave is received, as will be described.

Hence its angular position on the screen :32 in-' dicates the direction of reception of such waves.

The distance measuring circuits which control the radial displacement of the spot 16a from the center of the screen 132 comprise an oscillator I and a frequency modulator 2 connected to modulate the frequency of the oscillator to conform to the curve 3 of Fig. 1b. ihe frequency is caused to progressively decrease linearly with respect to time and'is then quickly restored to its" initial value and the cycle repeated.

The oscillator output is fed by lines 41, 48 to radiating dipoles of the antenna system l2 to produce a wave in the form of a directed beam which is radiated from the antenna system.

When reflected from a distant object the reflected wave is received by the antenna system i2 and is fed to a beat detector 44 where it is combined with energy fed directly from the oscillator I, to produce a beat note. If the radiated wave, for example, is of a frequency represented by the point B on the curve 3 the reflected wave will have the same frequency. At the time the reflected wave is received, however, the transmitted wave may have a frequency T. The distance RD (Fig. 12)) represents the time required for the emitted wave to travel to the reflecting object and return. Hence the beat frequency TD is a measure of the distance of such object.

The beat frequency in the detector 44 is converted, by an impulse generator 64, to an impulse having an amplitude proportional to the beat frequency.

The two-phase repeater I80, and the tube [6 are normally blocked so that no spot appears on the screen I32. The impulse from the impulse generator 6 is caused to unblock the repeater and to cause a potential to be applied to the deflector plates MI and I42 by the repeater which v is proportional in amplitude to said impulse but has a phase relationship determined by the repeater !8, thereby causing the spot 16a to be deflected radially by a distance proportional to the amplitude of the deflecting impulse which in turn is proportional to the distance of the reflecting object. At the same time, the impulse is applied to the control grid I39 of the tube l-G which unblccks said tube and causes the cathode ray to produce the spot Isa. The screen I32 may have One specific circuit which is suitable for the above purpose is shown in Figs. 2 and 4.

Referring to Figure 2 the antenna system I2 comprises a dipole radiator 21 which is mounted near the throat of a metallic horn casing 22. The base of the horn 22 is provided with an ad-' 4 justable piston 23 for tuning purposes. The two elements of the dipole 2| are connected by twoconductors 24 and 25 to two slip rings 21 and 26 which are engaged by two brushes 28 and 29. Secured to the horn shaft Si is a worm gear 32 which meshes with a worm 33 mounted on the shaft of a motor 35 which is driven at constant speed from any suitable source of power not shown. If found desirable a mechanism may be provided for disconnecting the Worm drive and providing a handle attached to the shaft 3|, which may be used for rotating the horn 22 manually.

The transmitter It includes an electron coupled oscillator 35 the frequency of which is determined mainly by the L and C Values of an inductance S5 and a condenser 31 and to a less degree by the capacitance of a variable condenser 38 which is mechanically operated by a cam 39 driven at constant speed by a motor 4|. The cam 39 is so designed that the capacity of the condenser 38 builds up gradually and linearly to a maximum and then upon release by the cam the capacity quickly becomes a minimum and immediately starts again to build up to a maximum, so that the oscillator frequency follows the curve 3 of Fig. 1b as above described,

The output circuit of the oscillator 35 is connected to a frequency doubler 42 including a tuning condenser 43, which doubles the frequency by tuning the plate circuit to double the oscillator frequency. The frequency doubler 42 is connected to a power amplifier 44 which includes a pentode the plate circuit of which is also tuned to the double frequency and includes the primary of a transformer the secondary of which is connected to the brushes 23 and 29 by conductors el and 48 of a transmission line.

If found desirable the slip rings 2621 and brushes 2329 may be replaced by a pair of ca- 'pacitors as shown in Figure 3 for transmitting the energy to the radiator. In this system two circular plates 5| and 52 are attached to but insulated from the shaft 3| and are connected to the two conductors 25 and 2 3. Surrounding the shaft 3! are five fixed circular plates 5351 which are provided with holes so that they do not touch the shaft 3!. The two fixed plates 53 and 54 are connected together and to the conductor 41, the two fixed plates 56 and 5! are connected together and to the conductor 48 and the fixed plate 55 is grounded. The plates 5l-51 are designed for constanc of capacity, so that the dielectric between the station plates 53-54 and 58-51 and the rotor plates 5! and 52 furnishes a frictionless and substantially electrically perfect substitute for the slip rings 26 and 21 for energy transfer purposes.

The power amplifier 44 also constitutes a beat detector the output circuit of which includes a condenser 69 across which is connected a filter circuit 6!. The filter circuit BI is connected thru a transformer 62 to the terminals 63 of an impulse generator 54, which is shown in more detail in Figure 4. This circuit may be of any well known type for converting variations of signal frequency to variations of signal intensity. The input terminals 63 are connected thru a filter circuit 65 (Fig. 4) and a transformer 66 to the input circuit of an audio amplifier 61. The output cir- .cuit. of'the amplifier 61 is connected to a limiter 58 which includes a pentode B9.

The output circuit of the limiter 68 is connected to the input of a tapered frequency discriminator tube 7| which amplifies higher frequencies more strongly than low frequencies which is accomplished by the choice of the coupling elements in the discriminator output circuit such ioke 3-2 in the plate lead and a coupling condenser '53, which is connectedfrom the plate of the tube i! to the input of a rectifier driver tube It. The rectifier driver tube I4 is connected thru a transformer T5 to a diode rectifier it, the transformer I5 being suitably designed to improve the frequency characteristics of the transmission from the grid of the discriminator amplifier II to the rectifier I6.

Two output condensers i1 and I3 are connected in the output circuit of the rectifier I6 and a motor driven switch I9 is provided for simultaneously grounding both of the condensers ii and it. The switch I9 may be operated in synchronism with the modulation cam 38; such as by direct mechanical connection. The inte: grated voltage output of the rectifier 76 is impressed upon an impulse tube 8| coupled by a condenser 82 to a load resistor 83 which is connected to the output terminals 84.

Secured to the shaft SI of the rotating horn system I2 shown in Fig, 2 are two elongated condenser rotor plates SI and 92 of nearly identical shape but with one displaced 90 degrees with respect to the other. Mounted adjacent to the two rotor plates 91 and 92 are two fixed plates 93 and which with the rotor plates 9i and 92 form two variable condensers which are formed and adjusted in such a manner that one condenser is at a maximum when the other condenser is at a mean value.

The variable condensers Gil-93 and 9295 are operativeiy connected to two oscillator triodes 95 and 85 which may be operating at different frequencies. The plates of the triodes 95 and 96 are shunt fed thru chokes 91 and S8 and are coupled thru blocking condensers 99 and IUI to the oscillatory circuits formed by coils I92 and I03 and main condensers I04 and I05. The main condensers I04 and I05 are paralleled by the variabie condensers ilk-93 and 92-454. Oscillations are produced by inductive coupling of grid coils I83 and it? to the coils I82 and I83 respectively.

Output connections are made at taps on the coils m2 and IE3 and are connected .to the first grids of two pentodes III and I I2 respectively. The third grids of the pentodes' I II and H2 are connected together and to the output terminals 84 of the impulse generator 64 and are normally biased beyond cut off by battery us. The plate circuits of the pentodes IiI and H2 are connected thru frequency discriminating transformers lid and IE5 to two sets of rectifiers III5-I II and II23I IE3 which are so connected in a back to back arrangement that the outputs are in opposition. The cathodes of the rectifiers II"! and IIS are connected to the grids of two triodes I2! and I22, the plates of which are connected to a resistor assembly comprising output resistors I23 and IN and a balancing potentiometer I25 the adjustable contact of which is connected to one side of a battery I25 the'othe'r side of which is connected to ground thru a condenser IZ'I. Connected across the battery I26 is a potentiometer I28 and the cathode biasing resistor I29.

The oscilloscope It is of standard and well known construction the details of which form no part of the present invention. The oscilloscope I6 is shown as comprising a glass tube ISI the upper end of which forms a fluorescent screen I32, the fluorescent material of which is of such a nature that it maintains its fluorescence for an appreciable time, .for example several seconds after being excited by the electron ray. In the tube ISI are mounted'the heater element I33 which is supplied with current thru a transformer I34 from anysuitable source I35, the cathode I35, which is connected to one side of the heat r I33, the control grid I31, the focusing electrode I33, the accelerating anode I39 and the two sets of deflection plates IAI and H52. One plate of each of the sets of deflection plates Iii and M2 is connected to the plates of the tubes I22 and Iii respectively. The other plates of the sets IM and I42 are connected to the anode I39 and to the ground.

For operating the oscilloscope IE a source of high potential is provided, which in this case is shown as a battery M4 shunted by a potential divider I45 provided with two adjustable taps I 38 and MI. The tap use is connected thru a con trol grid resistor I48 and condenser M9 to the control grid I31, which is connected thru two blocking condensers I5I and IE2 and two resistors I53 and I54 to one of the terminals 84 .of the impulse generator Iii. A limiter tube I55 is provided to cut down the impulse when it exceeds a value necessary to give good illumination.

The oscilloscope I5 is mounted in the steering wheel pedestal II the top I5I of which is circular in shape and forms the position indicator as shown in Fig. 5. Rotatably mounted in the .top plate IIiI is an annular ring IE2 in whit-his set a plate I63 of curved glass or other transparent material. Engraved in dotted lines on the glass plate (Fig. 5) are the points of the compass i-il l and concentric circles I 65 denoting distances from the center. Engraved on the fluorescent screen I32 are radial lines I56 denoting the lubber line of the vessel and lines making definite angles with the lubber line. Extensions of the lines 56 are engraved as lines It! to the top plate IEI. Secured to the under surface of the annular ring IE2 is a gear I68 which meshes with a pinion I39 mounted on the shaft of an electrical repeater III which is fastened to a bracket Il2 secured to the top plate IEI. The electrical repeater ii! is connected by a cable I13 to the electrical transmitter of the ships gyro compass and operates in a well known manner so as to cause the ring IE2 and glass plate I83 to act as a compass repeater.

In Figs. 6 and '7 is illustrated one type of re flecting system that may be .used in connection with the present invention. This reflecting system comprises a plurality of metalic rods I'li mounted vertically in one or more plates N2 of insulating material which are shown as support ed by two uprights I13. The rods i'II are of a length equal to half the wave length of the energy radiated by the dipole ZI and are so arranged that the intensity of energy reradiated from them will be substantially uniform in all directions in a horizontal plane.

In Fig. 8 is shown a plan view of a harbor in which the channel is indicated by the dotted lines I15. On one side of thischannel are a plurality of buoys [l5 and on the other side a plurality of buoys I'I'l. These'bucys may be provided with reflecting systems similar to those shown in Figs. 6 and 7. Similartypes of reflecting systems may be located at any desired places along the shore or at a lighthouse as indicated at I18. A vessel entering the harbor is indicated at I8I.

'In the operation of the-system describeda .vcssel I8I is provided with the transmitting system 7 12 which is rotated by the motor 34. This may be a complete rotation at a uniform speed as is shown in Fig. 2 or the horn 22 may be caused to sweep back and forth thru a restricted arc by any well known type of mechanism.

The electron coupled oscillator 35 produces energy the frequency of which is determined by the constants of the inductance 36 thefixed condenser 3'! and the variable condenser 38 which is varied by the rotation of the cam 39. The cam 39 is so designed that the capacity of the condenser 38 builds up gradually and lineally to a maximum and then upon release by the cam the capacity quickly drops to a minimum and then immediately starts to build up to a maximum again. The cam 39 is operated on a timing interval which is long in comparison with the time required for the radiant energy to be transmitted, reflected and received;

The output of the oscillator 35 is doubled in frequency by the doubler circuit 42 and is fed to the control grid of the pentode 45 the plate circuit of which is also tuned to the double frequency. The

output energy of the pentode 4521s fed thru the transformer 46 and over the transmission lines 4148 to the brushes Ell-29. thence thru the slip ringsZE-El and conductors 24-25 to the dipole radiator 2|.

If the capacitors l5l as shown in Fig. 3 are used instead of the slip rings 262'! the energy is transmitted to the rotating shaft electrostat" ically instead of by conduction. In this way a substantially electrically perfect substitute for the slip rings is provided which eliminates any disturbing effects produced by the motion of the slip rings under the brushes which in practice might cause considerable difficulty.

The energy radiated by the dipole 2| is directed in a concentrated beam indicated by the broken line !82, which sweeps around in a horizontal plane due to the rotation of the horn 22. When the beam I 52 impinges on the reflector I78 each of the rods Hi acts as a miniature radiator and reradiates the energy received in all directions. A small amount of this reradiated energy is received by the dipole 2| as indicated by the broken line I83. This received energy then passes back over the transmission line 47-48 to the transformer lib where it is fed into the plate circuit of the pentode 45. Here it is heterodyned with the current existing in the pentode 45 to produce a low frequency current the frequency of which corresponds to the distance of the reflector H8. The transmitter power supply must be substantially free from ripple because of the weakness of the received signals and the small magnitude of the low frequency currents produced by the heterodyning process.

These low frequency currents are impressed across the condenser 60 and are filtered by the filter circuit 6| to free them from undesirable high and low frequency currents. In this way signals reflected from greater distances than it is desired to cover by the visual position indicator may be eliminated. These low frequencies then pass thru the transformer 62 and are impressed upon the impulse generator 64.

The stray reflected disturbances from beyond the range of the oscilloscope are eliminated by the filter 65, Fig. 4, and the audio frequency signal after passing thru the transformer 66 is impressed upon the amplifier 61,. ,With the modulations of a linear saw tooth nature the tone corresponding to a reflector at a given distance is constant during the time that the fre- 8 quency is slowly varying. The noise or tone re sulting when the cam 39 quickly changes the capacity of the condenser 38 will be of a much higher pitch and is either blanked out by the 5 audio filter 65 or may be blanked out artificially by a mechanical connection from the cam 39 to the receiver which will prevent the tube of the amplifier 6! from amplifying when the cam 39 V is resetting the modulation to the normal linear nature.

The output of the amplifier 6"! is impressed upon the limiter 6B the action of which is the first step in processing the beat tone to make the impulse depend upon the frequency and not upon the strength of the beat note. As a result of this limiting action the output of the limiter is of constant level regardless of the input over a wide range of input levels. The limiter shown is symbolic of what can be accomplished with more perfect but more complex designs which are not a part of the present invention and are not here discussed.

The output of the limiter 68, which is of constant level, is impressed upon the tapered frequency discriminator tube H which amplifies the high frequencies more strongly than the low frequencies. This is accomplished by the choice of proper constants for the choke l2 and the con-- denser 73 which, in effect, constitutes a high pass filter which with the proper design can produce a fairly linear relation between input frequency and output signal strength when the strength of the input signal remains constant.

The output of the discriminator tube H is impressed upon the rectifier driver tube 74 the energy from which passes thru the transformer T5 to the diode rectifier T5. The design of the transformer 75 is such as to improve the frequency characteristics from the grid of the discriminator tube II to the rectifier 16. The rectifier 76 is of an integrating type with the voltage across the output condensers i1 and it gradually building up during the cycle of modulation. The output arrangement is such that the integrated voltage 4.5 is impressed upon the impulse tube 8!. The rate of rotation of the cam 39 is slow and the condenser 32 is sufficiently small so that there is little or no voltage transferred to the load resistor 83 while the charges on the condensers ll and 78 are building up. i

Impulses are created by the discharging of the condensers l1 and 78 by the rotary switch 19 which grounds both of the condensers simultaneously and resets the device for further operation. The switch '19 may be operated in synchronism with the cam 39. The voltage across the condenser 18 just prior to its discharge by the switch '19 is substantially proportional to the frequency impressed upon the input terminals 63 and is therefore proportional to the distance of the reflector I18 from the vessel IBI.

The impulse tube 8| is energized by the quick change of its grid voltage and the impulse on the 5 grid is transferred thru the output condenser 82 to the output terminals 84. As the charge on the grid condenser 18 increases to make the grid of the tube BI more positive the plate current is gradually increasing and the plate voltage decreasing. When the condenser is mechanically discharged the plate current drops to a small value, the plate becomes more positive and a positive surge or impulse passes to the output terminals 84. The general shape of this pulse is not dependent upon the input signal but the 9 strength is dependent solely upon the frequency of the input to the input terminals 63. V

In order to make the angular position of. the spot on the oscilloscope H correspond to the angular position of the horn 22, the two phase repeating device i8 is used for producing this efiect by entirely electrical means. As the shaft 3! rotates the two condensers SL423 and 92-94 are varied so that when one condenser is at a maximum the other will be at a mean value. As these condensers are operatively connected to the oscillators $55 and 96 the frequencies of these two oscillators will vary with the result that two currents are produced each frequency modulated.

Due to the design of the condenser plates the frequency modulations are sinusoidal but differ by 90 degrees so that when one oscillator is at a maximum or minimum the other is at a mean value.

The frequency modulated outputs of the oscillators 95 and 96 are impressed upon the first grid to ground circuits of the pentodes lit and H2 respectively. The third grids of the pentodes ill. and H2 are normally biased beyond plate currentv cut off so that energy from the oscillators 95 and 96 do not pass through the pentodes i i l and l :2 until the third grids are momentarily energized from the output of the impulse generator ti l. When this occurs the pentodes Hi and H2 operate as amplifiers and the plate circuits are actuated in accordance with the strength of the impulse.

Energy from the plates of the pentodes l l i and H2 passes thru the frequency discriminating transformers i it and H5 and operates into the two sets of rectifiers l iEl ll and l8j--l i9 which are so connected that the outputs are in opposition. This discrimination involves a double humped coupled circuit system so arranged, for example, that when the first grid'of the pent'ode iii is energized by a higher than average frequency the rectifier i ll is energized for the duration of the impulse on the third grid and when similarly energized by a lower than average frequency the rectifier i it is similarly energized. As a result of the back to back connection of the outputs the grid of the triode i2! is energized with a voltage which depends upon the frequency of the oscillator and therefore upon the angular setting of the shaft 35 and horn 22. In a similar manner the voltage on the grid of the triode 222 is dependent on the frequency of the oscillator 86 and therefore upon the angular setting of the shaft iii and horn 22.

It is thus seen that a two phase Voltage is produced on the grids of the two triodes Hi and E22 of a frequency corresponding to the rate of-' rotation of the shaft 35. The magnitude of these two voltages is dependent upon the strength of the impulse upon the third grids of the two pentodes Hi and i 52 from the impulse generator which has already been shown to be proportional to the frequency of the signal applied to the terminals 53. As this frequency is determined by the distance of the reflector H8 from the vessel :8! the magnitude of the voltages impressed upon the triodes l2l and 522 will be proportional to this "distance.

The two phase signal produced by the triodes l2! and l..2 are impressed upon the two sets of plates Q42 Mi respectivay of the oscillo scope to with one set of plates for each phase. Under these circumstances any spot of light produced on the fluorescent screen by the electron stream would describe. a circle with a radius proportional to the strengths of the two phase 10 signal, The degree of illumination of the spot depends upon the impulse.voltagefimpressed upon the control grid [31 which controls the strength 53 and blocking condenser E55 to the grid I31.

As the strength of this'inipulse var'es the limiter its is provided to prevent its exceedin a value necessary to give good illumination. The characteristics of this impulse are determined by the values of the condensers i5! and I52 and theresist'ers its and i154 which are so selected that the impulse will quick y produce the. required amount of illumination but the grid 31 does not return to normal so quickly when theoriginal impulse ceases.

It is thus seen that the impulse has two functions, first to determine how far from the center of the fluorescent screen I32 the spot of light will appear and second to cause the spot to appear by the action of the controlgrid The strengths of. the two phase signals on. the grids of the triodesl2! and H22 are dependent upon the strength of signal from the impulse generator 5d. These triodes operate as D. C. ampliflers using resistance coupling into the deflection plates i i! and M2. The battery 5-26. feeds. plate current thru the balancing. potentiometer 25 and output resistors i513. and 524 to the plates of the tridodes IZl. and I22 respectively. The two potentiometers Midland R8 are independently adjusted so that in the absence of signals the plates of the triodes l2! and IE2 and the oscilloscope plates MI and I62 are at ground potential, Thus in the absence of a signal the possible spot of light will be at the center of the fluorescent screen !S2. The centering of the possiblespot is accomplished by adjusting the position of the tap M6 of the potential divider Hi5 when there is no signal on the triodes t2] and H2.

When the device is operative, due to the reception of a signal reflected from the reflector H8, a spot will appear upon the fluorescent screen 32 at a distance from the'center depending upon the strength of the impulse from the impulse generator t l, which in turn is dependent on the distance of the reflector H3, and at an angular bearing corresponding to the position of the shaft 3! at the instant that the reflected signal is received.

It'is thus seen that a system is provided which will give a visible indication on the fluorescent screen i312 of the distance and angular bearing of the reflector H8 from the vessel I8l. The distance may be measured on the screen I32 by means of the concentric circles l55 (Fig. 5) and its angular position with respect to the center line of the vessel I81 by relation to the radial lines IE5 or its position with respect to thelpoints of the compass by its relation to the compass card markings 564 on the plate I63. The method of operations described permits the system to be operated'at a very slow speed if so desired.

It is to be understood that the method of producing the two phase currents at Very low frequencies and the method of producing variable signal strength proportional to frequency are shown for purposes of illustration and the invention is not limited to these methods for producing the desired results. Also other means for measuring the distance of an object may be employed such as that described in an article pub- 11 lished in the- Proceedings of the I. R. E., July 1938, pp. 848-858, Direct reading absolute altimeter.

In Fig. 9 is shown a modified form of transmitting and receiving apparatus. In this case a double horn I93 is mounted on the rotating shaft In this horn are mounted two sets of dipoles I84 and I 85. The dipoles I84 are connected thru slip rings or other means not shown to the secondary of the transformer 46, shown in Fig. 2, and the dipoles I85 are connected thru slip rings or other means not shown and thru a transformer I 99 to the input circuit of a pentode amplifier I81. The output circuit of the pentode I8! is connected thru a transformer I88 to the diode circuit of a diode-triode tube I89. The output circuit of the triode portion of the tube I89 is connected thru a transformer I9I to the input terminals 63 of the impulse generator 94 shown in Fig. 2.

Operation of Fig. 9

In the operation of modified form of the invention shown in Fig. 9 frequency modulated energy from the transmitter I4 is radiated by the dipole I 84. Vfhen this radiated energy strikes the reflector I'I8 some of it is reradiated back to the dipole I85 and is impressed upon the grid of the pentode amplifier I81 together with some of the energy received directly from the transmitter. The direct energy transfer from the transmitter to the grid of the pentode amplifier I81 may be obtained by inductive coupling between the transformers 56 and I36, or by any other well known means. Both of these energies are amplified in the pentode I31 and are impressed upon the diode portion of the tube I89 where they are rectified to produce an audio tone corresponding to the diiference of the transmitted and reflected frequencies. the triode portion of the tube I89 and is impressed thru the transformer I9I upon the input terminals '53 of the impulse generator 64. From here on the operation is similar to that described in connection with Fig. 2.

A modified form of combining circuit is shown in Fig. 10 in which the secondary of the transformer 46 is connected to a circuit including a variable condenser I94, a variable resistor I 95, the primary of the transformer 62 and two fixed condensers I95 and I91 which are shunted by the primary of a transformer I98. The secondary of the transformer I98 is connected to the transmission line ll-(I8.

Operation of Fig. 10

In the operation of the combining circuit shown in Fig. 10 energy from the transmitter I l passes from the secondary of the transformer 46 to the transformer I98 and thence over the transmission line 4'I48 to the dipole radiator 2|. A very small portion of the transmitter energy, depending on the setting of the variable condenser I94 and variable resistor I95, is allowed to pass to the receiver. This energy is combined with the received energy to produce energy of audio frequency which is impressed, thru the transformer 62, upon the input circuit of the impulse generator 6-5.

Another modified form of combining circuit is illustrated in Fig. 11 in which the secondary of the transformer 49 is connected to a circuit comprising an inductance 2IlI, two fixed condensers 292 and 293, two variable resistors 204 and 205 and the primary of the transformer 62. The

This audio energy is amplified by I reflectors 2| I--2 I 5.

Operation 0 Fig. 11

The operation of the modified combining circuit shown in Fig. 11 is similar to that shown in Fig. 10. Nearly all ofthe transmitter energy passes from the transformer 46 to the transmission lines 4'I48. A small portion of the transmitter energy, however, depending on the adjustment of the variable resistors 264 and 295 is combined with the received energy and the resultant audio frequency energy passes thru the transformer 82 and is impressed upon the impulse generator 64.

A modified form of reflecting system for giving a code signalmay be used as shown at 2H1 in Fig.8. In this form of the invention four refiectors 2| I, 2 I2, 2 I3 and 2M are provided that are essentially similar to the reflector illustrated in Figs. 6 and 7. A fifth reflector 2I5 is provided, which has an elongated shape, but otherwise is constructed in a similar manner to the other four. These reflectors may be located along the shore as shown or at any other suitable position.

In this type of indicating system it is desirable to have an audible signal produced in the pilot house and for this purpose the circuit shown in Fig. 12 is connected across the terminals 2I6, and 2 H of Fig. 2. This circuit comprises a triode 2I3 the output circuit of which includes the winding of a relay 2| 9. The back contact of the relay 2H3 is connected in circuit with a battery 22I, a buzzer 222 and a switch 223. The buzzer 222 may be located at any suitable place in the pilot house II.

Operation of Fig. 12

In the operation of this form of the invention the grid of the triode 2I8 is normally at ground potential thus causing current to flow thru the relay 2I9 the contact of which will remain open. The horn 22. (Fig. 2) is rotated at a slower rate than previously described. As the radiation from this horn 22 sweeps the reflecting system 2|!) reflected signals of various'length will be received corresponding to the horizontal dimensions of the These signals will cause a spot of light to appear upon the fluorescent screen I32 as previously described. They will also cause a negative potential to be applied to the terminal 2H5 and thus to the grid of the triode 2I8. This negative potential will decrease the current flowing thru the relay 2| 9 which will be de-energized. This will cause the back contact to close, which in turn will close the circuit from the battery 22! thru the buzzer 222, which will be sounded.

In this way not only will a spot of light appear on the fluorescent screen I32 to indicate the position of the reflecting system 2M, but an audible signal will be produced in the pilot house I I which will give the code signal of the reflecting system 2Ill, which in this case is dot, dash, three dots so that the navigator may identify the particular reflecting system by this means.

A modified form of reflecting system is shown in Figs. 13 and 14 in which the metallic rods III are mounted in two plates 226 and 221 the former being rigidly secured to two uprights 228. The plate 221 is carried by two crossheads 229 which are mounted for vertical motion in two grooves 23I provided in the uprights 228. Springs 232 are mounted in the grooves 23I and tend to hold the crossheads 229 and plate 221 in their lowest position.

Secured to the cross heads 229 are pins 233 to 13 which are pivoted members 234 which are mounted for vertical motion in brackets 235 attached to the uprights 228. Rotatably mounted on the lower ends of the members 234 are rollers 236 which engage cams 23l, which in turn are secured to the ends of a shaft 238 rotatab-ly mounted in the uprights 223i Secured to the shaft 238 is a worm wheel 238 which meshes with a worm 24I carried on the shaft of a motor 242 mounted on plate 243. The motor 242 is driven at constant speed from a suitable power supply 254. The cam 231 is provided with two short notches 245 and 245 and one long notch 241.

Operation of Figs. 13 and 14 In the operation of the reflecting system shown in Figs. 13 and 14, the motor 242 drives the cams 23? at a fairly slow speed by means of the worm 25 I, gear 239 and shaft 238. In the position shown in the figures the rollers 236 are in the notches 245 so that the late 221 together with the corresponding rods Ill are in their lowest position. As the cams 21: rotate the rollers 235 will ride up on the elevation between the notches 2 35 and 2%, thus elevating the plate 221 until at the highest point the rods Ill on the plate 22'! engage corresponding rods III on the plate 226. As the cams 23l rotate further the rollers 235 move down into the notch 248 thus causing the two sets of rods Ill to be disengaged.

In this way the two sets of rods Ill are alternately engaged and disengaged the length of time and the spacing of the intervals when they are disengaged being determined by the shape and location of the notches M5, 246, and 221. In the example shown in Fig. 14 there would be two short intervals and a long interval followed by a considerable space.

{hen the two sets of rods Ill are separated they are tun-ed to the wave length of the energy radiated by the dipole 2! of Fi 2 and will act as re-radiators of this energy, as already explained. When the two sets of rods are in engagement. however, they are detuned to this wave length and will not reradiate this frequency.

In the operation of this system the horn 22, shown in Fig. 2 is rotated manually until during its rotation it points directly at the reflector shown in Fig. 13 at which time a signal will be received back from the reflector and will cause the buzzer 222 to operate indicating the fact that the reflector has been picked up. The horn 22 is thereafter maintained on the reflector and the buzzer 222 will be caused to operate every time that the two sets of rods III are separated. In this way the buzzer 222 will be caused to emit a signal corresponding to the notches cut on the cam 23'l, which in this case is two dots and a dash. The location of the reflector will be indicated on the fluorescent screen I32 as already described.

In this manner the position and identity of the reflector may be determined. These detuning reflectors may be located at any desired point such as on buoys and will serve to identify the particular buoy in a manner similar to the way buoys are at present identified by a specific series of flashing lights.

In passing up a channel it may be desirable to be able to differentiate the buoys on the left side of the channel from the buoys on the right side and have this difference indicated on the position indicator shown in Fig. 5. This may be accomplished by the use of two directional 14 horn antenna systems and two sets of transmitters and receivers each of which would radiate a different frequency modulation, such for example as L and R.

The buoys I76 (Fig. 8) on the left side of the channel may be provided with reflectors which are tuned to the L frequency and the reflectors on the buoys Ill on the right are tuned to the R frequency. The signals reflected from the buoys I'ifi are received by the receiver tuned to the L frequency and operate an L oscilloscope in a manner previously described. The signals reflected from the buoys Ill are received by the receiver tuned to the R frequency and operate an R oscilloscope.

The operation of the selective reflector is indicated in Fig. 8 in which the L frequency energy from the vessel Isl is indicated by the line 25! and the reflected L frequency energy from the buoy Ilfi is shown by the line 252. The R frequency energy is indicated by the m... line 253, but as this i not reflected from the buoy I'I6 there is no corresponding line shown returning to the vessel I8I. The reverse action is shown in connection with the buoy Ill where the L frequency energy is indicated by the line 254 and the R frequency energy by the line 255. The reflected R frequency energy is shown by the line 256. The two L and R, cscilloscopes may be so arranged in conjunction with a system of mirrors or prisms that the two spots of light on the fluorescent screens of the two oscilloscopes may be projected on a single viewing screen. The fluorescent screen of the L and R Oscilloscopes may be coated with suitable materials so that the spot On the L oscilloscope screen appears red and the spot on the R oscilloscope appears green. This effect may also be accomplished by the use of red and green color filters.

In this way the positions of the buoys on the left side of the channel are indicated by red spots on the screen and the buoys on the right side of the channel are indicated by green spots on the screen, thus clearly indicating the location of the channel.

A modified form of reflector is depicted in Fig. 15 which is so designed that the radio waves received by it are reflected in a given direction. This reflector is preferably constructed of a plurality of rods 26! similar to the rods III of Figs. 6 and 7 which are mounted in a plate 262 of insulating material supported by uprights 263. The rods are preferably arranged in a straight line 264 and spaced a wave length apart.

Operation of Fig. 15

In the operation of the reflecting system illustrated in Fig. 15 if the transmitted wave impinges upon the series of rods 25! in a direction indicated by the line 265 which is perpendicular to the line 2% then the reflected waves from all the rods ZSI will be in phase and a maximum of reflected energy will be reflected back along the line 2'65. If the transmitted energy strikes the rods 26! in any other direction than perpendicular to the line 264 the energy reflected from the various rods 2$l will be of different phase and will not produce a maximum effect.

If a set of the rods 25I forming a directional reflector is mounted as indicated at 263 in Fig. 8 the line 26! perpendicular to the set of rods 26I will be the line of maximum reflection or range of the reflector 265. As shown in Fig. 8 the vessel IBI is on this line and therefore the receiving system will receive a signal of maximum intensity indicating that the vessel is on the range 267. The vessel I86 may then proceed up the channel Hit by following this range until it arrives at the point 258 which is opposite a second directional reflector 253 the range of which is indicated by the line 2H. At the point 268 the receiving system on the vessel 18! will receive a strong signal reflected from the directional refleet-or 253 thus indicatingthat the vessel 58! has reached the point 258 where it is no longer safe to follow the range 261. The vessel l8! will then pick up another range 212 from a directional reflector not shown and will proceed up the new course in the channel F55. In this way a vessel may proceed up a channel in dense fog by the use of a series of radio reflection ranges. W

In Fig. 16 is illustrated a system for identifying vessels and their direction of travel by means of radio reflection. In this system a vessel 2 is equipped with a plurality of reflectors as indicated at Elli-418. The arrangement of these reflectors may indicate the type of vessel on which they are mounted, such for example as a cruiser, merchantman, destroyer, etc.

Operation of Fig. 16

In the operation of the system depicted in Fig. 16 as the beam of radiation from the horn 22 sweeps across the vessel 21d some of the radiation will be reflected back to the horn 22 and will pro duce a pattern on the fluorescent screen I32 corresponding to the arrangement of the reflectors 215-?58. This pattern will indicate not only the type of vessel which for example may be a cruiser but also the direction in which the vessel is travelling. Thus if the pattern shown on the screen I32 is it will indicate that the vessel'Z'M is travelling to the left and if the pattern shown is it will indicate that the vessel is headed to the right.

Other types of vessels may be equipped with different arrangements of reflecting systems. Thus, for example, a merchantman might have the arrangement and a destroyer m It is thus seen that by means of this system not only the type of vessel but its direction of heading may be ascertained.

Although only a few of the various forms in which this invention may be embodied have been I shown herein, it is to be understood that the invention is not limited to any specific construction but be embodied in various forms without departing from the spirit of the invention as defined bythe appended claims.

What is claimed is:

1. A navigational guide system for vessels comprising a directional radio beam radiator, an oscillator feeding said radiator, frequency modulation means modulating said oscillator to cause the radiated waves to vary in frequency in a predetermined manner, means rotating said radiator for causing said beam to sweep an area, a remote reflector in said area selective to said beam and adapted to reradiate the same when energized thereby, a receiver on said vessel responsive to said reradiated beam and including a combining circuit for combining the received wave with the transmitted wave to obtain therefrom a beat frequency which constitutes a measure of the distance to said remote reflector, a converter circuit converting said beat frequency into impulses modulated in amplitude in accordance with variations in said beat frequency, repeater mechanism responsive to the rotational movement of said radiator, and indicator mechanism responsive to said amplitude modulated impulses to indicate the varying amplitude thereof as a measure of the distance to said remote reflector and responsive to said repeater to indicate the angular position of said radiator when said impulse is obtained,

2. A navigational guide system for vessels comprising a directional radio beam radiator, an oscillator feeding said radiator, frequency modulation means modulating said oscillator to cause the radiated waves to vary in frequency in a predetermined manner, means rotating said radiator for causing said beam to sweep an area, a remote reflector in said area selective to said beam and adapted to reradiate the same when energized thereby, a receiver on said vessel responsive to aid reradiated beam and including a combining circuit for combining the received wave with the transmited wave to obtain therefrom a beat frequency which constitutes a measure of the distance to said remote reflector, a converter circuit converting said beat frequency into impulses modulated in amplitude in accordance with variations in said beat frequency, repeater mechanism responsive tothe rotational movement of said radiator, and indicator mechanism responsive to the combined effect of said repeater mechanism and'said amplitude modulated impulses to indicate the amplitude of said impulse and the angular position of said radiator at the instant of said impulse.

3. A navigational guide system for vessels comprising a directional radio beam radiator, an oscillator feeding said radiator, frequency modulation means modulating said oscillator to cause the radiated waves to vary in frequency in a predetermined manner, means rotating said radiator for causing said beam to sweep an area, a remote reflector in said area selective to said beam and adapted to reradiate the sam when energized thereby, a receiver on said vessel responsive to said reradiated beam and including a combining circuit for combining the received wave with the transmitted wave to obtain therefrom a beat frequency which constitutes a measure of the distance to said remote reflector, a converter circuit converting said beat frequency into impulses modulated in amplitude in accordance with variations in said beat frequency, repeater mechanism responsive to the rotation movement of said radiator and an indicating device comprising a cathode ray oscilloscope having means to deflect said ray in a controlled circular path about a center point, circuits controlled by said repeater mechanism to cause said ray to follow in its circular path the rotational movement of said radiator, circuits actuated by said amplitude modulated impulses to deflect said ray radiall by an amount proportional to the amplitude of said impulses, and circuits responsive to said impulses to produce said ray only at the instant of said impulses whereby a spot is produced thereby displaced from said center point by a distance and in a direction corresponding to that of said remote reflector.

4. A navigational guide system for Vessels comprising a directional radio beam radiator, an oscillator feeding said radiator, frequency modulation means modulating said oscillator to cause the radiated waves to vary in frequency in a predetermined manner, means rotating said radiator for causing said beam to sweep an area, a remote reflector in said area selective to said beam and adapted to reradiate the same when energized thereby, a receiver on said vessel responsive to said reradiated beam and including a combining circuit for combining the received wave with the transmitted wave to obtain therefrom a beat frequency which constitutes a measure of the distance to said remote reflector, a converter circuit converting said beat frequency into impulses modulated in amplitude in accordance with variation in said beat frequency, an indicating device comprising a cathode ray oscilloscope having a control electrode for controlling the emission of said ray and pairs of angularly disposed deflector electrodes for controlling the angular displacement of said ray from a central point, repeater mechanism responsive to the angular position of said radiator and connected to energize said deflector electrodes to cause said ray to take an angular position corresponding to the orientation of said radiator, means normally applying a biasing potential to said control electrode to block A the emission of said ray, and means connecting said converter circuit to said repeater and to said control electrode to apply to said electrode a potential suited to unblock said tube to cause said ray to be emitted and to apply to said repeater a potential corresponding to the amplitude modulation of said circuit, whereby the ray is defiected by said deflector electrodes a radial distance proportional to said amplitude modulation and in a direction corresponding to the orientation of said radiator at the instant the reflected wave is received.

5. A system as set forth in claim 4 in which said repeater includes amplifier tubes connected to apply a potential to said deflector electrodes which varies in phase with th radiator position and said converter circuit is connected to control the operation of said amplifier tubes in accordance with the impulse amplitude.

6. In a system as set forth in claim 3, a rotatably mounted scale associated with said oscilloscope to indicate the deflection of said spot and means for orienting said scale to designate compass directions.

7. A system as set forth in claim 1 in which said converter circuit comprises an amplifier circuit, an output limiter device to produce a constant amplitude frequency modulated current, a frequency discriminator circuit converting said frequency modulated current into a corresponding amplitude modulated current, and an impulse circuit energized by said last current to produce impulses varying in amplitude in accordance with said amplitude modulations.

8. A navigational guide system for a vessel, comprising a plurality of sources of different directional radio beams on said vessel each adapted to be rotated to sweep an area, frequency modulation means for modulating each of said sources to cause said beams to vary in frequency in a predetermined manner, a plurality of remote reflectors in said area comprising two groups, each group being selective only to one of said beams and adapted to reradiate the same when energized thereby, said reflectors constituting left and right course markers having different reradiating characteristics, a plurality of receivers on said vessel each responsive to said reradiated beams having one of said characteristics and including circuits responsive to the time lag between said radiated and said corresponding reradiated beams, and indicating mechanism actuated by said circuits, said indicating mechanism having means to indicate both the direction of each of said reradiated beams and the distance of each of said reflectors from said vessel.

9. A navigational guide system for a vessel comprising a plurality of directional radio beam radiators, a plurality of oscillators each feeding one of said radiators, frequency modulation means modulating each of said oscillators to cause the radiated waves to vary in frequency in a predetermined manner, means rotating each of said radiators for causing said beams to sweep an area, a plurality of remote reflectors in said area each selective to one of said beams and adapted to reradiate the same when energized thereby, said reflectors constituting left and right course markers having different reradiating characteristics, a plurality of receivers on said vessel each responsive to said reradiated beams having one of said characteristics, and each including, in combination, a combining circuit for combining one of the received waves with a corresponding one of the transmitted waves to obtain therefrom a beat frequency which constitutes a measure of the distance to one of said remote refiectors, a converter circuit for converting said beat frequency into impulses modulated in amplitude in accordance with variations in said beat frequency, repeater mechanism responsive to rotational movement of one of said radiators, and indicator mechanism responsive to said amplitude modulated impulses to indicate the varying amplitude thereof as a measure of the distance to one of said remote reflectors and responsive to said repeater to indicate the angular position of one of said radiators when said impulse is obtained.

10. A system of the type described in claim 1 characterized in that said combining circuit includes a bridge network electrically interposed between said oscillator, said directional beam radiator and said receiver; said network providing predetermined direct energy transfer from said oscillator to said receiver.

11. A system as defined in claim 1 wherein said remote reflector includes means periodically rendering the same inoperative whereby the operative periods form identifying signals.

12. A system as defined in claim 1 wherein said remote reflector is normally tuned to reradiate a predetermined received beam and contacting means for detuning said reflector periodically in accordance with a selected code to form identifying signals.

JOHN HAYS HAMMOND, JR. 

